Ash and tephra from Mount Shasta

During Holocene time Mount Shasta erupted pumiceousdacitetephra twice about
10,000 years ago. One deposit is more than 0.1 km3 (0.024
mi3) in volume and the other is less than 0.1 km3; both lie
mainly east and within about 50 km (31 mi) of the volcano. Lithicash has been
erupted at Mount Shasta many times during the last 10,000 years and the deposits
mantle the ground surface within about 25 km (15.5 mi) of the summit.

Based on this recent behavior, it is not likely that Mount Shasta will erupt very
catastrophic volumes of tephra and ash in the near future. However, smaller
eruptions are possible. If a future eruption of tephra and ash occurs, areas
downwind and near the volcano (within about 50 km or 31 mi) will be most affected.
The degree of risk from air-fall tephra decreases progressively as the distance
from the volcano increases.